----- Received 11 September 2006; revised 24 january 2007; accepted 01 February 2007 ----- Description of the larva of Somatoch/ora margarita (Odonata: Corduliidae) John C. Abbott 1 & Clem~ Mynhardt 2 1 Section of Integrative Biology, Brackenridge Field Laboratory, University Station #C7000, The University ofTexas at Austin, Austin, Texas 78712, USA. <[email protected]> 2 Department of Entomology & Museum of Biological Diversity, The Ohio State University, 1315 Kinnear Rd., Columbus, OH 43212, USA. <[email protected]> Key words: Odonata, dragonfly, 5omatochlora margarita, 5. Filosa, 5. provocans, larva, description. ABSTRACT The larva of Somatochlora margarita is described from a specimen reared from the egg to the final stadium. The larva, previously unknown, is morphologically similar to the larvae of S. calverti, S. filosa, S. ozarkensis, and S. provocans. Combinations of diagnostic characters are given for distinguishing these species. Growth of this species is discussed with respect to other species of Somatochlora and Odonata. INTRODUCTION Somatochlora margarita Donnelly has arguably the most restricted distribution of all the North American Somatochlora. It is known from the long-leaf and loblolly pine forests of southeast Texas and northern Louisiana. For nearly 30 years this species was only known from its type locality in the Sam Houston National Forest (San Jac­ into Co., Texas), but Price et al. (1989) expanded its initial range to a now estimated 16,000 km2 area in east Texas. It has also now been found in northern Louisiana (Abbott 2001, 2005). Adults can be locally abundant, but are generally not well rep­ resented in collections. The larva has remained undescribed until now. The terminal stadium is described here from a larva reared from eggs collected from a gravid fe­ male. The female was collected northwest of Shepherd in San Jacinto Co., Texas. To our knowledge, the larva has not been collected in the wild to date. The larval stage of 24 of the 26 known species of Somatochlora occurring in North America has been described (Cashatt & Vogt 2001; Steffens & Smith 2006). The two remaining species areS. calverti Williamson & Gloyd and S. margarita. The pri­ mary author is in possession of the larvae of S. calverti and is preparing a formal de­ scription. We present preliminary characteristics of that species and describe the larva of S. margarita comparing it to other known Somatochlora larvae in this paper. All exuviae associated with the reared final stadia were examined. Notes on the growth of this species and early stadia are also included. International Journal of Odonatology 10 (2) 2007: 129-136 129 -------------Abbott & Mynhardt ------------- MATERIAL AND METHODS The description is based on one final stadium female larva reared from egg to final stadium by S.W. Dunkle. Eggs were collected from a female, 23 June 1985, by S.W. Dunkle, USA, Texas, San Jacinto Co., NW of Shepherd in Sam Houston National Forest (Fig. 1). Eggs hatched 30 September 1985. All larvae were preserved in 80% ethanol. Dimensions are given to the nearest 0.1 mm and were made with an ocular micrometer. We did not examine all of the exuviae obtained from early stadia of S. margarita, nor did we quantify most char­ acters for these stages. In some cases the exuviae were destroyed by the prey items in the vials with the larvae or by the larvae themselves. The final stadium female is shown in Figure 2. All material referred to in this description is deposited in the Brackenridge Field Laboratory Insect Collection at the University of Texas at Austin. Figure 1: Distribution of Somatochlora margarita - showing seven counties in Texas and Louisana where this species has been reported. 130 International journal of Odonatology 10 (2) 2007: 129-136 -------------The larva of Somatochlora margarita ------------- Figure 2: Somatochlora margarita larva- dorsal view; scale line 5 mm. International journal of Odonatology 10 (2) 2007: 129-136 131 ------------Abbott & Mynhardt ------------- LARVAL DESCRIPTION The larva of S. margarita is elongate with a total length of 19 mm, moderately covered with hairs, and generally pale in coloration (Fig. 2). The head is twice as wide as long with small eyes that are slightly elevated. The abdomen is oval and slightly wider than the head. S. margarita appears most similar to S. provocans. Head: Width 6.0, widest at eyes; about twice middorsal length 3.1. Lateral margins behind eyes broadly convex, converging posteriorly at concave occiput. Frons and occiput with dense, coarse setae. Antennae 5.2 in length. Segments 1-7 with lengths of 1.0, 0.9, 0.9, 0.5, 0.5, 0.7, and 0.6 respectively. Segments uniformly colored pale throughout, with segments 1 and 2 densely clothed with coarse setae. Segments 3-7 sparsely clothed with fine setae. Labium pale extending posteriorly to level of meso­ coxae. Prementum 4.8 at greatest width; anterior margin angulate with edge slightly concave. Palps triangulate with 8 crenulations each bearing a cluster of 5-8 spiniform setae of varying lengths; dorsal setae numbering 3-4 twice as long as ventral setae. Lateral margin clothed with fine, dense setae. Palpal setae 9 with 18-20 fine spicules posterolaterally. Premental setae numbers 11 (Fig. 3 ). Thorax: Widens posteriorly, not quite reaching width of head (ratio 3:2.8). Protho­ rax with dorsolateral protuberances and margins of prothorax bearing short, coarse setae. Lateral margins proximate to procoxae bearing long, fine setae; pterothorax with dorsal ridges and short, coarse setae medially. Lateral margins bearing long, Figure 3: Somatochlora margarita larva- (a) prementum showing lateral and premental setae, dorsal view; (b) abdomen, lateral view; (c) closeup of left labial palp showing crenulation and associated setae; (d) terminal appendages, dorsal view. 132 International Journal ofOdonatology 10 (2) 2007: 129-136 The larva of Somatochlora margarita Table 1. Characters of larval stadia 2-13 in Somatoch/ora margarita. - Total: total length; Theol: theoretical length, obtained by dividing the total length of stadium 13, 19 mm, succes- sively by 1.26; PalpS: pal pal setae; PremS: premental setae; Wings: number of abdominal seg- ments the hindwing sheath extends,+ indicates presence of wing sheaths,- indicates absence. Stadium n Total [mm] Theol [mm] PalpS PremS Wings 2 12 1.2-1.5 1.5 0 1 3 5 1.9-2.3 1.9 1-2 2-3 4 6 2.5-3.1 2.4 2-3 3-5 5 7 3.2-3.8 3.0 2-3 4-5 6 5 4.0-4.6 3.8 3-4 5-6 + 7 7 5.2-6.2 4.7 4-5 6-8 + 8 5 6.6-7.4 6.0 4-5 8-9 1-2 9 6 8.0-8.8 7.5 5-6 8-9 2 10 2 9.1-9.2 9.5 6 9-10 2-3 11 10.8 12 7 10 3 12 16.9 15.1 8 11 4 13 19 19 9 11 6 fine setae; longest at anterior and posterior margins. Prosternum bearing short, stout setae on anterolateral protuberances. Mesosternum larger than metasternum; both with well-developed anterolateral protuberances bearing long setae. Legs uniformly tan; coxae and trochanters densely clothed with short setae. Length of metafemur 6.5; length of metatibia 6.5. Hw sheath 6.3 long, extending just past anterior edge of 56. Abdomen: Oval in general shape, widest at 55-7. Length measured along the ventral midline including the terminal appendages, 11.4; maximum width in ventral view 7.7. Dorsum glabrous except for posterior margin of each tergite armed with a row of 7-12 short, coarse setae, centered each side of the midline. Lateral margins with dense setae becoming long and hair-like on 58-10; setae on 59 and SlO extending past paraprocts for a distance equal to length of paraprocts. Venter of abdomen glabrous. Middorsal hooks acute and falciform occurring on 54-9 (Fig. 3). A vestigial hook may be present on 53. Largest middorsal hooks on 57 and 58. Middorsal hook on 59 extends just short of the midpoint of SlO. Lateral spines on 58 and 59; apices di­ rected posteriorly. Lateral margins with short, dense setae; those on 58 approxi­ mately half the length of 59. Spines on 58 0.6 length of those on 59 and 0.2 length of margin of 58 (anterolateral to posterolateral corners of sternite). Spines on 59 0.3 length of margin of 59 (anterolateral to posterolateral corners of sternite). Epiproct acuminate extending well beyond distal ends of cerci; lateral margins distinctly con­ cave; length 1.3. International journal of Odonatology 10 (2) 2007: 129-136 133 -------------Abbott & Mynhardt------------- DISCUSSION Among North American Somatochlora species, the presence of prominent middorsal hooks on the middle abdominal segments separates S. margarita from the 12 species that lack these hooks. Four of the 14 species that have middorsal hooks (see Cashatt & Vogt 2001 ), S. calverti, S. filosa, S. ozarkensis Bird, and S. provo cans Calvert, are most similar to S. margarita (Table 2). Of these four species, S. margarita can be dis­ tinguished from S. calverti and S. filosa by the shorter and broader lateral spines on S9. InS. calverti and S. filosa these spines are twice or more long as wide. The two remaining species, S. ozarkensis and S. provocans each have 7-8 palpal setae while S. margarita has 9. Larvae of many species of Somatochlora are often hard to collect due to their re­ stricted habitats (Cashatt & Vogt 2001). Several species including S. ensigera Mar­ tin (Huggins 1983) and S. filosa (Dunkle 1977) have been described based on reared final stadium larvae and in some cases exuviae. Cashatt & Vogt (2001) provided a key to all known North American Somatochlora larvae.